Photometer



March 31, 1936. A. GOUDSMIT ET AL PHOTOMETER Filed. June 1, 1935 2Sheets-Sheet 1.

)ZENTORS ATTORNEYS March 31, 1936. A. GOUDSMIT ET AL PHOTOMETER 2Sheets-Sheet 2 Filed June 1., 1935 ///////////z Ill/I/lI/I/l. 7IIIIIIIIIIIIIIIIIIIIII/III INVENTORS MO /LQLM ATTORNEYS Patented Mar.31, 1936 UNITED STATES PATENT OFFICE acsimt rno-rous'raa ArnoldusGoudsmit, New York, and William H.

Summerson, Jackson Heights, N. Y.

Application June 1, 1935, Serial No zhiflll 13 claims. (o1. sax-44) 1ocomparatively simple form of construction and conveniently usable.Another object is to provide an instrument wherein the possible sourcesof error may be compensated for by a simple form a of adjustment andthereby increase the dependl abilityand accuracy of the instrument.Another object is to avoid the human error that arises 4 when attemptingto judge the intensity of light by the. eye. Another object is toprovide an instrument whereby the use of graphs and calibrai go tioncurves is limited to those solutions which do not show the theoreticalrelationship between concentration and light absorption. Another objectis to provide an instrument of such a degree of precision that a minimumof successive mess-- g5 urements is required, and wherein theconcentration of a solution to be tested may be computed as of theinstrument; Fig. 2 is an enlarged vertical section on the line 2-2 ofFig. i; Fig. 3 is a front elevation showing the scale plate; Fig. 4

is a horizontal section on the line 4-4of Fig. 1;

Fig. 5 is a horizontal section on the line 56 of 40 Fig. l; and Fig. 6is a diagram of the electrical connections. I

The instrument is based upon the principle of causing light from acommon source to pass through each of the two solutions to be compared45 and adjusting the depth of one solution, through which the lightpasses, relatively to the depth of the standard solution through whichthe light passes, until equivalent amounts of light are transmittedthrough the two different depths of 60 solution. The intensity of thetransmitted light through the two solutions is measured by responsivemeans in the form of photoelectric cells.

Such cells generate electromotive forces in accordance with the amountof light to which they 68 are exposed; and by relating the electromotiveforces of two cells to each other and by use of a sensitive instrument,such as a galvanometer. in

- such a way as to be responsive to any difference between theelectromotive forces of the two cells, it is apparent that aftersuitable adjustment of 5 the beamof light going through one solution inrespect to the one. going'through the other, a condition can be attainedin which the galvanometer will show a zero reading. Thus by adjustingthe depth of the solution to be tested until the 10 light transmittedther'ethrough is equivalent to the-light transmitted through thestandard solution, as shown by the zero reading of the galvanom'et'ei',the scale readings showing the depth of the two solutions will be ameasure of the relai5 tive concentration of the two solutions. Thismethod of comparison gives high sensitivity, as

change of-light through one solution to an amount of less than one tenthof one percent of the total light intensity, may usually be detected.Stability go is insured by using a common source of light and asimultaneous comparison of the light transmittedthrough the twosolutions. Any momentary change in the light source will simultaneous lyand similarly aifect both cells and thus introduce no material error dueto change of voltage of the light source. such as a lamp bulb derivingits voltage from the usual lighting supply circult.

Referring to the. drawings; the instrument is mounted upon a base Iwhich supports an upwardly extending box-like frame 2. At the top of theframe is mounted a horizontally extending bearing 3 which carries aneccentrically mounted support 4 for the lamp bulb 5 which is the source85 of light for the instrument. The support 4' may be turned in thebearing 3 for adjusting the position of the filament of the bulb inrelation to the light receiving portion of the instrument; and thebearing 3 may also be moved in the supporting frame 2 for similarlyadjusting the position of the light bulb filament. Set-screws 6 serve toretain the parts in fixed position after adjustment. A cylindrical hood5a is secured to the frame 2 and encloses the bulb 5 for confining thelight of and for shielding the bulb 5, opening to being formed in thetop of the hood and provided with an upwardly dis-placed cover toprovide ventilation for dissipating the heat prism. These plungers arehollow and carry glassroot two .beams of light downwardlythroughthesolutionstobetestedaswillbelaterexplained At thetopof framelismoimtedthelenspicce I for receiving the rays from the source anddirecting them downwardly to strike the two sides of the apexofprism 8.Acylinder llisrotatably mounted at its lower end on the .top of frame Iand encloses the lens I and is likewise rotatably mounted at its upperend in the lower part of thetubela. Acylindricalsupportllisheld withinthe upper end of the tube II and projects through an opening in thelower partof the shield la and carries a ground glass plate Ila throughwhich light from the bulb I is transmitted. Within thetubellisaiixedtube I2 of slightly smaller diameter and which has an downwill now be described. On the front of the opening on its side. The tubell likewise has anopeningonitssidesothatwhenthetube Ills rotated, thetwo openings may coincide for the purpose of inserting or removing lightfilters, as may be desired. The tube ii is afterwards turned onits axisso as to close the openings.

The frame 'I is provided with a removable cover plate Ia asshown in Fig.2 and carries on its inner surface a leaf spring Ib for the purpose ofyieldably holding the prism 8 against the inside surface of the frame I.On the opposite sloping sides of the frame I are locat..d two adjustablethumb-screws lo, the inner ends of which impinge against the sides ofthe prism 8. It is evident by loosening one of the screws lo and turningthe other to move inwardly, the prism 8 may be adjusted horizontally toone. side or the other for the purpose of compensating for errors ofmanufacture, as hereinafter explained.

Apairofplungers I3 and Iiaareilxedinposition at their upper ends by ascrew connection with openings in the bottom of frame I which openingsare below the two surfaces la of the plates Ilb at their lower ends.These plates are sealed to the endsof the plungers to preventtheentrance of any fluid within them. The two parallel paths of light raysfrom the faces at of the prism pass downwardlythrough the plung-' era Itand Ila respectively and through'the glass plates Ilb to lower portionsof the apparatus. 'I'hetubes I2 and Ilaareopaquetotheentrance ofextraneous light and it is apparmt that the only light which passesthrough the plates Ilb, is that derived from the bulb I and whichpassesthrough the ground glass a, lens I, prism l and thence through the tubesI2 and Ila.

The plungers extend within a pair of cups Ila which are removablysupported at their lower ends in circular receptacles I lb. One side ofthe receptacles is slotted and the cups carry pins Ilc at their lowerends which are adapted to drop into the slots and thereby hold the cupsin definite positions in the receptacles. Secured to the lower end ofeach of the receptacles isa circulardisc II from each of which depends acylinder IIa havingitsupperendsecuredtothedlsc Ilbyapin and slot bayonetioint Ilb.

Fitted within the cylinders Ila are a pair of cylinders IIsecuredinilxedpositiontothebase I. The upper ends of cylinders 'll carryphotoelectric cells II from eachofwhichapairofflexible leads I'Iaextend\downwardly and out through an opening I whereby the indicatingcircuit.

The lower ends of the cups I4, Ila carry glass discs Md which are sealedto prevent the escape of fluid therefrom. Opposite the plates I Id areaggro lower end of the cylinder y be connected to an outside directlyover the photoelectric cells II. The cups openings lie in the discs II.These openings are moved and adjusted vertically with reference to theirrespective plungers I2, Isa and are also adaptedto be adjustedrelatively to each other. During the upward or downward movement ofthese parts. the cylinders Ila slide over the cylinders I. by a closeflt and thereby prevent any extraneous light from entering and affectingthe photoelectric cells. The cups I4, Ila are opaque to the entrance oflight and consequently the only light which strikes each of thephotoelectric cells is that which passes downwardly through theirrespective plungers, cups and openings Ilic.

The mechanism for moving the cups up and frame 2, as shown in Figs. 2and 4, is mounted a cylindrical frame extending crosswise to the frame2. The frame 20 is seated in cutout portions of the frame 2 and held inposition by a screw 20a which extends through the rear portion of theframe 2 and is threaded into a mid portion of the frame 20. Within theframe 20 is a pair of bearings 20b which journal a pair of shafts 20c.

Milled knobs 20d, adapted to be turned manually are secured to the outerends of the shafts 2lc. Each of the shafts 200 have aiilxed thereto apinion 2lle. Within the frame 2 and. at the right and left ends thereofare mounted vertically slideable plates 2|. These plates are nicelyfitted within the frame 2, and have inwardly projecting portions 2Iaupon the front surfaces of which are racks 2 lb. The pinions 2Ierespectively engage with the racks 2| b and it is evident thatturningthe knobs 22d will cause the plates 2| to move up and down asindividually adjusted by the user.

Secured to each of the plates 2| at rear thereof is a plate 22, as areshown in Figs. 4 and 5. These plates are slideable againstthe inside ofthe hack of the frame 2 and each is marked on its front 'face with ascale as indicated in Fig. 3. Between the two plates 22 and securedtothe back of the frame 2 is another plate 23 of comparatively shortlength having a zero reading and a vernier scale at each edge thereof,in juxtaposition to the scales of the plates 22, as shown in Fig. 3. Onthe face of 'theframe 2 and just above the manual adjusting means,already described. is an opening 2 covered by .a glass plate 24a whichplate is carried by a frame 24b secured to the face of the frame 2. Thisopening or window is opposite the fixed scale plate 23 whereby .anobserver may conveniently read the scale plates 22 with reference to thefixed scale 22. A reflecting mirror 24c, as shown in Fig. 2, is fixedwithin the frame 2 and is inclined with its lower edgenear the scaleplates and its upper edge .at the lower edge of the window plate 24a.Within the top portion of the box frame 2 is another oppositely inclinedmirror 24d; and opposite this mirror is an opening 24s to the interiorof the light cylinder to. Light from the bulb 5 passes through opening24c and strikes the mirror 24d where it is reflected downwardly to themirror 240 which reflects the light upon the scales for illuminating thesame.

A vertical slot 2!, as shown in Fig. 5 is formed at each side of theframe 2. A bracket 25a is seecured to each of the slideable plates 2i.as shown in the left-hand portion of Fig. 5 and the brackets aremoveable with the plates 2i in the slots 25.

From the bases which hold the cups ll, Na, ex-

tend arms 28b which are in turn secured to the brackets 25arespectively. as shown in the lefthand portion of Fig. 5. It is evidentthat when the left-hand knob 20d is turned, its scale plate 22 will bemoved relatively to the flxed scale plate 28 and that the cup Ila willbe moved relatively to the plunger its; likewise when the right-handknob 20d is turned. its scale plate and cup ll will be movedaccordingly. Thus the scale readings of the plates 22 with reference tothe zero reading of the fixed plate 23 will show the relative depths ofthe fluids between the ends of the plungers and the bottoms of the twocups.

The leads Ila from the photoelectric cells are connected so that thecells are in series with each other, as shown in Fig. 6. A galvanometer26 is connected across the leads connecting the cells with the usualswitch or tap key 280, as likewise shown in Fig. 6. It is evident thatwith this form of connection, each cell tends to pass a current throughthe galvanometer in a direction opposite to that of the other cell.Obviously when the current output of one cell is equal to that of theother, there will be no deflection of the galvanometer 26.

In using the instrument the standard fluid solution is placed in eachcup, and one of the cups, such as cup I4, is adjusted to a desirableposition. After suitably adjusting the prism and the other cup asdescribed and for reasons, which will appear. later until thegalvanometer 28 shows a zero reading, the standard solution is removedfrom cup I4 and replaced by the solution to be tested. The position ofcup is is then adjusted until thelight transmitted and imposed upon eachof the photoelectric cells II is such that the galvanometer 26 againshows a zero reading.

Under this condition of equivalent transmission of light through the twocompared fluids, the relative concentration of the two solutions will beshown by the relative depths through which the light is transmittedwhich in turn is directly shown by the relative readings of the plate 22associated with cup ll with reference to the zero reading of the flxedscale plate. It is evident that any unknown fluid or medium may bequickly and quite accurately tested with reference to a standard fluidor medium by this simple and direct method. V 1

As previously described the prism l is adjustable horizontally by meansof the thumb-screws 10. This is for the purpose of compensating forslight variations of the difl'erent parts in the course of manufacturesuch as in the lens 8,

ground glass Ila, prism 8 and its different surfaces. position of thebulb 5 and for differences in the photo-electric cells I! and in theassembly of the parts. The adjustment is made by placing portions of oneof the solutions under examination in each of the cups II and Ila. Theknobs 20d are then adjusted until the scale readings show the same depthof fluid between the ends,

of the plungers and the bottoms of the cups.

'lig t source I. as may be-caused by change of potential of the sourceof electromotive force. will equally affect the two paths of lightthrough the two fluids and consequently have no affect on theircomparison. The bulb 5 may be a usual six volt lamp connected to theusual lighting supply circuit with a suitable transformer, or

resistance, or other means introduced for reducsource, means fordividing the light in two paths through two fluid media .to be compared,means for adjusting the relative depths of the media through which saidlight is transmitted. and light sensitive responsive means forindicating when the light transmitted through the two media is ofequivalent amount. 7 I I j I 2 A' photometer comprising a common light.isource, means for dividing the light in two paths through two fluidmedia to be compared, means for adjusting the relative depths of themedia through which said light is transmitted, and

balanced light sensitive responsive means for indicating when the lighttransmitted through the two media is of equivalent amount.

3. A photometer comprising a common source of light, means for dividingthe light in twopaths through two fluid media to be compared, means foradjusting the relative depths of the media through which said light istransmitted, photoelectric} Qcells simultaneously receiving the lighttransmitted through said media, and a responsive device connected incircuit with said cells for indicating when the light transmittedthrough said media is'ofequivalent amount.

4. A photometer comprising a common light source, means for dividing thelight in two paths through two fluid media to be compared, means foradjusting the relative depths of the media through which saidlight istransmitted, means for adjusting the relative amount of light directedin said two paths, and light sensitive responsive means for indicatingwhen the light transmitted through the two media is of equivalentamount.

5. A photometer comprising a common light source, means for dividing thelight in two paths through two fluid media to be compared, means foradjusting the relative depths of the media through which said light istransmitted, a scale for directly reading the relative adjusted depthsof the two media, and light sensitive responsive means for indicatingwhen the light transmitted through the two media is of equivalentamount.-

6. A photometer comprising a common light source, a device for dividingthe light in two paths through two fluid media to be compared, meansior'adjusting the relative depths of the media through which said lightis transmitted. li ht sensitive responsive means iorindicating whenthelighttransmittedthroughthetwomediais or equivalent amount, and meansfor adjusting said device for changing the relative amount o lightdirected in said two paths.

7. A photometer comprising a common light source, a prism for dividingthe light in two paths through two fluid mediate be'compared,

means for holding the media in the light paths,

means for adjusting the relative depths o! the media through which saidlight is transmitted. light responsive means subjected to the lighttransmitted through said media for indicating when the light transmittedthrough the two media is of equivalent amount, and means'ior adjustingsaid prism for changing the relative amount of light directed in saidtwo paths.

8. A photometer comprising a vertical frame.

a source of light at the top of the frame, a prism below said source fordirecting the light in two .paths downwardly through the two fluid mediato be compared, flxed plungers through which a source or light at thetop 01 the frame, a prism below said source for directing the light intwo paths downwardly through the two fluid media to be compared, flxedplungers through which said two paths of light are transmitted,vertically adjustable cups for holding the media to be com-.- pared insaid light paths and enveloping said plungers, a scale for showing therelative depths oi the media to be compared, photoelectric cells belowsaidcups'subjected to the light transmitted through saidmedia, andindicating-means for showing when the electromotive force of said cellsis balanced. v

10. A photometer comprising a common light source directing light in twopaths through two fluid media to be compared, means tor adjustingthedepth of the medium through which said light is transmitted in one path,and light sensitive responsive means for indicating the comparativeamoimt of light transmitted through the two media. Y 11. Aphotometercomprising a commonlight source directing light in two pathsthrough two media to be compared, means for adjusting the depth of themedium through which said light is transmitted in one path, and lightsensitive responsive means for indicating when the light transmittedthrough thetwo media gives a bal anced eflect. 1 a

12. A photometer comprising a common light source directing light in twopaths through two fluid media to be compared, means for adjusting thedepth of the medium through which said light is transmitted in one path.photoelectric cells simultaneously receiving the light transmittedthrough said media, and a responsive device for indicating when thelight transmitted through the two media gives a balance efl'ect.

13. A photometer comprising a common light source directing light in twopaths through two fluid media to be compared, means for adjusting therelative amount of light directed inthe two paths, means for adjustingthe depth of the medium through which said light is transmitted in onepath, and light sensitive responsive means for indicating when the lighttransmitted throughthe two media gives a balanced ei!ect.

ARNOLDUS GOUDSMIT. WILLIAM H. SN.

has

